EP4368409A1 - Security element, security document and method for producing a security document - Google Patents

Abstract

The invention relates to a security element (11) for use in a security document (10), comprising a preferably calendered metal fabric and/or a metal foil (5) provided with individualizing holes, in the surface (3) of which a structural element (21) is introduced, which consists of a laser-induced periodic microstructure. The invention further relates to a security document (10) with such a security element (11) and a method for producing the security document (10).

Description

The present invention relates to a security element for use in a security document. The invention also relates to a security document and a method for producing a security document.

To increase the security against forgery of security documents, especially valuable documents, different features and processes are used that make it difficult or impossible to copy or falsify them. A security document is usually made up of several layers that are preferably bonded together by lamination. The data to be inserted to personalize the document is inserted under a preferably transparent cover layer within the material to protect it from manipulation. This can be achieved by laser personalization in the otherwise finished data carrier. Another process provides for the data carrier to be provided with a preferably transparent cover layer after personalization.

A valuable or security document can be falsified by removing the cover layer and, after manipulating the underlying data, applying a new cover layer. Holograms can be used to protect the document from manipulation, as described in the publications WO 2017 109 119 A1 , EN 10 2007 042 386 A1 , EP 2 738 624 B1 described. For this purpose, a special hologram foil is exposed accordingly and applied to the data carrier. Furthermore, the surface of a security document can be microstructured, which makes any manipulation of the cover layer recognizable. Another possibility is described in the publication EP 1 970 211 A1 The document is marked on the narrow side surfaces with a laser to create an optical connection between the layers. In the printed documents WO 98/19869 or. DE 697 23 283 T2 A security feature is presented in which information is introduced into several layers of the document by perforating the data carrier.

Most of the known processes process one layer or the surface of the document with a process that generates a feature with a specific appearance. By separating the layers or treating the surface, it is possible to change or replace one appearance. Perforation, which affects several layers of the document, is also a feature with a specific appearance, for example in the form of holes, which also weakens the stability of the document.

The following definitions are taken from the publication EP 2 738 624 B1 As already defined there, in the context of the present invention, a security element is understood to be a structural unit that includes at least one security feature. Security elements serve to protect security documents, which also include value documents, against forgery or copying. A security feature can be an independent structural unit that can be connected, for example glued, to a security document, which can also be a value document. However, it can also be an integral part of a security document. A security feature is a structure that can only be produced or reproduced without authorization with increased effort compared to simple copying, or not at all.

Security documents typically have a substrate, a print layer and optionally a transparent cover layer. A substrate is a carrier structure onto which the print layer with information, images, patterns and the like is applied. Materials for a substrate include all standard paper and/or plastic-based materials. Examples of security documents are identity cards, passports, driving licenses, ID cards, Access control cards, visas, tax stamps, tickets, vehicle documents, banknotes, cheques, postage stamps, credit cards, any chip cards and adhesive labels.

Against the background described, the object of the present invention is to further improve the forgery security of security elements and security documents.

This object is achieved by a security element for use in a security document according to claim 1, by a security document according to claim 4 and by a method for producing a security document according to claim 7. The dependent claims contain further advantageous embodiments of the invention.

The security element according to the invention is designed for use in a security document, for example as a component or as a layer arrangement in the context of a security document.

The security element comprises a preferably calendered metal fabric, into the surface of which a structural element is introduced, which consists of a laser-induced periodic microstructure. Such laser-induced periodic surface structures form optical gratings, which can be used to produce structural colors, among other things, which is why they are particularly suitable as elements for protecting security documents against forgery. The laser-induced periodic microstructure thus forms the optical grating, which allows an individual color image to be recognized depending on the lighting and viewing angle. When the microstructured metal fabric is laminated, it is typically enclosed by the material of the card body, so that the security element provided with the laser-induced periodic microstructure cannot be removed from the laminated card body without causing damage.

As an alternative to a metal mesh, a metal foil, which is preferably provided with individual holes, can be used. The individual holes ensure that the bond with the surrounding layers and the individualization or personalization of the hole arrangement increases the security against counterfeiting.

The at least one structural element with its periodic microstructure can be arranged on the surface and/or in the surface and/or in the interior of a layer. Preferably, at least one structural element comprises a number of individual structural components, which can be designed, for example, as depressions, for example in the form of holes and/or elevations and/or cavities and/or pixels, for example colored pixels. The at least one structural element in any case has a periodic structure that is formed by a number of structural components. The use of periodic structures makes it easier to detect manipulations and thus enables a quick check of the authenticity of a security document.

A "microstructure" is understood to mean the sequence of structural components with dimensions of less than 100 micrometers (100 µm), in particular less than 10 micrometers (10 µm), preferably less than 1 micrometer (1 µm). The smaller the dimensions, the more difficult it is to counterfeit or tamper with the security element. The distance between the structural components is also preferably less than 100 micrometers (100 µm), in particular less than 10 micrometers (10 µm), preferably less than 1 micrometer (1 µm).

The structural elements and/or structural components of the structural elements are produced using "ultra-short" laser pulses, for example with a pulse duration of less than 10 picoseconds (10 ps), in particular less than 1 picosecond (1 ps) or less than 500 femtoseconds (500 fs). In particular, laser structures in the micro- or nanometer range can be produced relatively easily using ultra-short laser pulses. The use of ultra-short laser pulses enables precise production and efficient production of the structural elements. In particular, ultra-short laser pulses minimize or prevent thermal or mechanical damage to the structural elements during processing. With a suitable choice of processing parameters, almost melt-free processing with high precision is possible. Due to the short interaction time of the ultra-short Laser pulses with the material do not cause the material to change in color. On the other hand, a specific appearance, such as a color change of the structural elements, can be created by carefully selecting the processing parameters.

Preferably, the laser-induced periodic microstructure is introduced using ultrashort laser pulses, with a periodicity of between half the wavelength of the laser beam and the entire wavelength of the laser beam being present or used. This allows a characteristic periodic structure to be formed on the metal surface. This structure is abbreviated to LSFL (=LSFL for "low spatial frequency laser-induced periodic surface structure").

However, it is also possible to provide a different structure, which is achieved, for example, when the laser-induced periodic microstructure is introduced using ultrashort laser pulses, with a periodicity of less than half the wavelength of the laser beam being present or used. This creates a characteristic periodic surface structure. This structure is abbreviated to HSFL (= HSFL for "high spatial frequency laser-induced periodic surface structure").

In a particularly advantageous variant, the security element is designed for a specific security document or for a specific type of security document with specific security information and a structure of the structural elements contains security information and/or personalized data, i.e. information that can be assigned to the holder of the security document, for the specific security document. The security against forgery is thereby increased.

The security document according to the invention is made up of a number of layers, preferably two or more layers. It comprises a previously described security element according to the invention. The security document according to the invention has the features and advantages mentioned above in connection with the security element according to the invention. It can in particular comprise laminated layers. The security document can be For example, it could be an identity card, a passport, a driving license, a company ID or another security document.

The microstructured metal fabric and/or microstructured metal foil provided with individualizing holes is preferably integrated into the layer structure of the security document, with the security element being covered on both sides by at least one of the layers. In this way, it is possible that the security element cannot be removed or detached from the layer structure or the layer composite without causing damage. The destruction of the layer composite or the security element indicates an undesirable attempt at manipulation.

To provide additional security for the security document, it has proven to be advantageous if the security document contains person-specific and/or document-specific reference information on one of its layers and if a structural element has a shape that corresponds to the reference information or that reproduces the reference information. In this way, it is possible to conclude without great effort that the layers or the structural element with the microstructured metal mesh are forged.

The advantages, advantageous embodiments and effects described in connection with the security element according to the invention and the security document according to the invention are achieved in this way by the method according to the invention.

• Bereitstellen eines vorzugsweise kalandrierten Metallgewebes, insbesondere in Form einer Folie und/oder einer mit individualisierenden Löchern versehenen Metallfolie
• Strukturieren der Oberfläche des Metallgewebes und/oder der mit individualisierenden Löchern versehenen Metallfolie mit einer periodischen Mikrostruktur mittels ultrakurzer Laserpulse, wodurch ein Strukturelement gebildet wird,
• Einlegen des mikrostrukturierten Metallgewebes und/oder der mit individualisierenden Löchern versehenen mikrostrukturierten Metallfolie zwischen wenigstens zwei Schichten, und
• Verpressen der Schichten mit dem mikrostrukturierten Metallgewebe und/oder mit der mit individualisierenden Löchern versehenen mikrostrukturierten Metallfolie zu einem Schichtaufbau, wodurch das Sicherheitsdokument gebildet wird.

The method for producing a security document as described above comprises in particular the following steps:

• Providing a preferably calendered metal fabric, in particular in the form of a foil and/or a metal foil provided with individualizing holes
• Structuring the surface of the metal mesh and/or the metal foil provided with individualizing holes with a periodic microstructure by means of ultrashort laser pulses, thereby forming a structural element,
• Inserting the microstructured metal fabric and/or the microstructured metal foil provided with individualizing holes between at least two layers, and
• Pressing the layers with the microstructured metal mesh and/or with the microstructured metal foil provided with individualizing holes to form a layer structure, thereby forming the security document.

Preferably, the microstructured metal fabric and/or the microstructured metal foil provided with individualizing holes is laminated at high pressure and at high temperature into a card body consisting of individual layers under a transparent cover film.

In order to create a characteristic structural element and thus a specifically specified security element, it has proven advantageous if the pulse energy of the laser beam is adjusted, regulated or changed during or during the structuring of the surface.

Alternatively or additionally, it is possible to adjust, regulate or change the pulse duration of the laser beam during or during the structuring of the surface.

Alternatively or additionally, it is possible to adjust, regulate or change the polarization of the laser beam during or during the structuring of the surface.

For further individualization of the security element and the microstructure in the surface of the metal mesh and/or the microstructured metal foil provided with individualizing holes, it is alternatively or additionally provided that the laser wavelength of the laser beam is adjusted, regulated or changed during or during the structuring of the surface.

Alternatively or additionally, the laser fluence of the laser beam is adjusted, regulated or changed during or during the structuring of the surface.

Preferably, the laser-induced periodic microstructure is introduced by means of ultrashort laser pulses, whereby the periodicity of this microstructure is between half the wavelength of the laser beam and the entire wavelength of the laser beam; thus, it is introduced into the metal surface in the form of LSFL (= LSFL for "low spatial frequency laser-induced periodic surface structure").

Alternatively, it is possible to introduce the laser-induced periodic microstructure using ultrashort laser pulses, whereby the periodicity of this microstructure is less than half the wavelength of the laser beam; thus, it is introduced into the metal surface in the form of HSFL (= HSFL for "high spatial frequency laser-induced periodic surface structure").

When creating the structural elements, the metal surface can be moved relative to a focused laser beam and/or scanned by a focused laser beam. The movement of the metal surface relative to a focused laser beam preferably takes place in an x-y plane. Scanning can be done using movable mirrors. There is the advantageous possibility that the angle of incidence of the laser beam is changed with respect to the surface normal of the metal surface during or during the structuring of the surface.

Further features, properties and advantages of the present invention are described in more detail below using embodiments with reference to the attached figures. All features described so far and below are advantageous both individually and in any combination with one another. The embodiments described below are merely examples which do not, however, limit the subject matter of the invention.

The figures are not necessarily detailed and to scale and may be shown enlarged or reduced in size to provide a better overview. Therefore, functional details disclosed here are not to be understood as limiting, but merely as an illustrative basis which the person skilled in the art can use to this field of technology provides guidance for employing the present invention in a variety of ways.

Fig. 1

zeigt schematisch die Herstellung eines Sicherheitselements durch eine Laserstrukturierung eines Metallgewebes in Form einer Metallfolie und/oder einer mit individualisierenden Löchern versehenen Metallfolie, wobei der ultrakurz gepulste Laserstrahl koaxial mit der Oberflächennormale der Metalloberfläche ausgerichtet ist,

Fig. 2

zeigt schematisch die Herstellung eines Sicherheitselements durch eine Laserstrukturierung eines Metallgewebes in Form einer Metallfolie, und/oder einer mit individualisierenden Löchern versehenen Metallfolie wobei der ultrakurz gepulste Laserstrahl unter einem von Null verschiedenen Winkel bezüglich der Oberflächennormalen der Metalloberfläche ausgerichtet ist,

Fig. 3

zeigt beispielhaft die laserinduzierte periodische Oberflächenstruktur nach einer Laserbehandlung im Sinne der Figuren 1 oder 2,

Fig. 4

zeigt schematisch die Herstellung eines Sicherheitsdokuments mit einem Sicherheitselement, das mit einer laserinduzierten periodischen Oberflächenstruktur gebildet ist, und

Fig. 5

zeigt ein fertiges Sicherheitsdokument, welches mit einem Sicherheitselement gebildet ist, das mit einer laserinduzierten periodischen Oberflächenstruktur versehen ist.

As used herein, the term "and/or" when used in a series of two or more elements means that any of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, if a composition is described as containing components A, B, and/or C, the composition may contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

Fig.1

shows schematically the production of a security element by laser structuring of a metal fabric in the form of a metal foil and/or a metal foil provided with individualizing holes, wherein the ultrashort pulsed laser beam is aligned coaxially with the surface normal of the metal surface,

Fig.2

shows schematically the production of a security element by laser structuring of a metal fabric in the form of a metal foil and/or a metal foil provided with individualizing holes, wherein the ultrashort pulsed laser beam is aligned at an angle other than zero with respect to the surface normal of the metal surface,

Fig. 3

shows an example of the laser-induced periodic surface structure after a laser treatment in the sense of Figures 1 or 2 ,

Fig.4

shows schematically the production of a security document with a security element formed with a laser-induced periodic surface structure, and

Fig.5

shows a finished security document formed with a security element provided with a laser-induced periodic surface structure.

In the Figures 1 and 2 , by way of example and not to scale, the production of a security element 11 for use in a security document 10 is shown. The security element 11 comprises a preferably calendered metal fabric and/or a metal foil 5 provided with individualizing holes, into the surface 3 of which a structural element 21 is introduced, which consists of a laser-induced periodic microstructure that is introduced with a laser beam 100 made up of ultrashort laser pulses.

The periodicity of the microstructure introduced by means of ultrashort laser pulses is, for example, between half the wavelength of the laser beam 100 and the entire wavelength of the laser beam 100, so that a laser-induced periodic microstructure is created in the metal surface 3 (LSFL). Alternatively, the periodicity of the microstructure introduced by means of ultrashort laser pulses is less than half the wavelength of the laser beam 100 (HSFL). The periodicity of the microstructure is in any case in the submicrometer range, with the microstructure forming an optical grating.

The laser beam 100 is operated with predetermined parameters. During laser processing, the pulse energy, the pulse duration, the polarization, the wavelength of the laser radiation and the number of pulses per area ("laser fluence") can be controlled and regulated.

Figure 2 refers to the possibility that the angle of incidence of the laser beam 100 can also be specified, changed and also regulated. For this purpose, it is indicated that the surface normal 4 of the metal surface 3 is displaced so that the laser beam 100 runs at a specified angle with respect to the surface normal 4 and is tilted with respect to the surface normal 4.

In Figure 3 is a high-resolution representation of the laser-induced periodic microstructure, thus the surface 3 in the area of the structural element 21 to recognize.

• Bereitstellen des vorzugsweise kalandrierten Metallgewebes und/oder einer mit individualisierenden Löchern versehenen Metallfolie 5,
• Strukturieren der Oberfläche 3 des Metallgewebes und/oder einer mit individualisierenden Löchern versehenen Metallfolie 5 mit einer periodischen Mikrostruktur mittels ultrakurzer Laserpulse, wodurch das Strukturelement 21 gebildet wird (Figur 1, Figur 2),
• Einlegen des mikrostrukturierten Metallgewebes und/oder der mit individualisierenden Löchern versehenen mikrostrukturierten Metallfolie 5 zwischen wenigstens zwei Schichten 1, 2, und
• Verpressen der Schichten 1, 2 mit dem mikrostrukturierten Metallgewebe und/oder der mit individualisierenden Löchern versehenen mikrostrukturierten Metallfolie 5 zu einem Schichtaufbau, wodurch das Sicherheitsdokument 10 gebildet wird.

In Figure 4 a method for producing the security document 10 with a security element 11 is illustrated. It comprises the following steps:

• Providing the preferably calendered metal fabric and/or a metal foil 5 provided with individualizing holes,
• Structuring the surface 3 of the metal fabric and/or a metal foil 5 provided with individualizing holes with a periodic microstructure by means of ultrashort laser pulses, whereby the structural element 21 is formed ( Figure 1, Figure 2 ),
• Inserting the microstructured metal fabric and/or the microstructured metal foil 5 provided with individualizing holes between at least two layers 1, 2, and
• Pressing the layers 1, 2 with the microstructured metal fabric and/or the microstructured metal foil 5 provided with individualizing holes to form a layer structure, whereby the security document 10 is formed.

The pressing of the structured metal fabric and/or the microstructured metal foil 5 provided with individualizing holes with the further layers 1, 2 of the security document 10 is preferably carried out under high pressure and at high temperature, so that an inseparable laminate, thus an inseparable card body, is created, in the interior of which the security element of the microstructure is embedded.

In Figure 5 the security document can be seen in which the security element 11 with the microstructured metal mesh and/or the microstructured metal foil 5 provided with individualizing holes is embedded. Depending on the viewing angle and the angle of illumination, a viewer sees a colored image that was created by the structural element 11 with the periodic microstructure. Here, it is possible that one of the layers 1, 2 is provided with person-specific and/or document-specific reference information, and that the structural element 21 has a shape that corresponds to the reference information or reproduces the reference information. This increases the forgery security of the security document 10 thus formed.

The color perceived by the viewer depends not only on the viewing and lighting angle but also on the parameters used to create the microstructure. This allows different color areas to be generated next to each other in a targeted and locally defined manner, which together produce a color image, whereby the color impression of the image changes depending on the viewing and lighting angle. Unlike the spectral color splitting of a grid, the colors are locally differentiated here, since a large number of grids are generated depending on the processing parameters of the metal surface.

The security element 11 according to the invention and the security document 10 according to the invention are therefore characterized by improved protection against counterfeiting, wherein the security element 11 can no longer be removed non-destructively from the composite of the card body of the security document 10, so that manipulations can be verified quickly and easily.

LIST OF REFERENCE SYMBOLS

1

layer

2

Top layer

3

surface

4

Surface normal

5

Metal mesh, metal foil with individualized holes

10

Security document

11

Security element

21

Structural element

100

laser beam

Claims (15)

Security element (11) for use for a security document (10), comprising a preferably calendered metal fabric and/or a metal foil (5) provided with individualizing holes, in the surface (3) of which a structural element (21) is introduced, which consists of a laser-induced periodic microstructure. Security element (11) according to claim 1, characterized in that the laser-induced periodic microstructure is introduced by means of ultrashort laser pulses, wherein a periodicity of the microstructure of between half the wavelength of the laser beam (100) and the entire wavelength of the laser beam (100) is present. Security element (11) according to claim 1, characterized in that the laser-induced periodic microstructure is introduced by means of ultrashort laser pulses, wherein a periodicity of the microstructure is smaller than half the wavelength of the laser beam (100). Security document (10) which has a layer structure made up of a number of layers (1, 2), characterized in that it comprises a security element (11) according to one of claims 1 to 3. Security document (10) according to claim 4, characterized in that the security element (11) is integrated into the layer structure, and that the security element (11) is covered on both sides by at least one of the layers (1, 2). Security document (10) according to one of claims 4 to 5, characterized in that person-specific and/or document-specific reference information is present on one of the layers (1, 2), and that the structural element (21) has a shape which corresponds to the reference information or which reproduces the reference information. A method for producing a security document (10) according to any one of claims 4 to 6, comprising the steps: - providing a preferably calendered metal fabric and/or a metal foil (5) provided with individualizing holes, - structuring the surface (3) of the metal fabric and/or the metal foil (5) provided with the individualizing holes with a periodic microstructure by means of ultrashort laser pulses, whereby a structural element (21) is formed, - inserting the structured metal fabric and/or the microstructured metal foil (5) provided with individualizing holes between at least two layers (1, 2), and - Pressing the layers (1, 2) with the structured metal mesh and/or the structured metal foil (5) provided with the individualizing holes to form a layer structure, whereby the security document (10) is formed. Method according to claim 7, characterized in that during or at the time of structuring the surface (3) the pulse energy of the laser beam (100) is adjusted, regulated or changed. Method according to claim 7 or 8, characterized in that during or at the time of structuring the surface (3) the pulse duration of the laser beam (100) is adjusted, regulated or changed. Method according to one of claims 7 to 9, characterized in that during or during the structuring of the surface (3) the polarization of the laser beam (100) is adjusted, regulated or changed. Method according to one of claims 7 to 10, characterized in that during or at the time of structuring the surface (3) the laser wavelength of the laser beam (100) is adjusted, regulated or changed. Method according to one of claims 7 to 11, characterized in that during or during the structuring of the surface (3) the laser fluence of the laser beam (100) is adjusted, regulated or changed. Method according to one of claims 7 to 12, characterized in that during or during the structuring of the surface (3) the angle of incidence of the laser beam (100) is changed with respect to the surface normal (4) of the metal fabric and/or with respect to the metal foil (5) provided with individualizing holes. Method according to one of claims 7 to 13, characterized in that the laser-induced periodic microstructure is introduced by means of ultrashort laser pulses, wherein the periodicity of the microstructure lies between half the wavelength of the laser beam (100) and the entire wavelength of the laser beam (100). Method according to one of claims 7 to 13, characterized in that the laser-induced periodic microstructure is introduced by means of ultrashort laser pulses, wherein the periodicity of the microstructure is less than half the wavelength of the laser beam (100).

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